Polymers and their use in asphalt compositions and asphalt concretes

ABSTRACT

A modified asphalt composition comprising a naphthenic asphalt, and a high-vinyl block copolymer is presented. The modified asphalt composition is prepared by combining a naphthenic asphalt and a high-vinyl block copolymer. Further an asphalt concrete is presented, such concrete comprises an asphalt, a functionalized block copolymer, and a siliceous aggregate. A diblock copolymer is presented, such copolymer comprises a vinyl block comprising conjugated vinyl aromatic units, a diene block comprising conjugated diene units and substantially devoid of a tapered block section between the vinyl block and the diene block wherein the diblock copolymer comprises a vinyl content of at least about 20%, and a molecular weight of at least about 50,000.

This application references Provisional Application No. 60/615,438,filed on Oct. 2, 2004. The entire disclosure of this referencedprovisional application is hereby incorporated by reference.

FIELD OF THE INVENTION

This invention relates to polymers and their use in asphalt compositionsand asphalt concretes.

BACKGROUND OF THE INVENTION

It is known to combine bitumen compositions, particularly asphaltcompositions, with aggregate to form compositions that are useful in thepreparation of road surfaces. The mixture of asphalt and aggregate maybe referred to as asphalt concrete. The asphalt serves as a binder forthe aggregate. Interaction between the binder and the aggregate istherefore desirable.

The asphalt may itself be reinforced or modified with a polymer. Thepolymer can improve many properties of the asphalt such as penetration,softening point, toughness, tenacity, and heat resistance. Knownpolymers or polymeric additives include symmetric radical blockcopolymers comprising arms having diene polymer blocks and vinylaromatic polymer blocks; block copolymers of a monoalkenyl aromatichydrocarbon monomer and a conjugated diolefin; olefin homopolymers andcopolymers, particularly i-butene homopolymer and copolymer; andisoolefin homopolymers.

While asphalt concretes have proven useful in the preparation of roadsurfaces, failure is, however, inevitable. Failures generally occurthrough bleeding, fatting up, cracking, and chip loss. The time untilfailure varies with several factors such as the amount and weight oftraffic and various weather factors such as temperature and rainfall.Unfortunately, failure frequently occurs at shorter time intervals thandesired.

There is therefore a continued need to improve the asphalt compositionsand asphalt concretes.

SUMMARY OF THE INVENTION

In general the present invention provides a modified asphalt compositioncomprising a naphthenic asphalt, and a high-vinyl block copolymer.

The present invention further provides a modified asphalt compositioncomprising the product of combining a naphthenic asphalt, and ahigh-vinyl block copolymer.

The present invention still further provides a method of preparing amodified asphalt composition comprising combining a naphthenic asphaltand a high-vinyl block copolymer.

The present invention further includes an asphalt concrete comprising anasphalt, a functionalized block copolymer, and a siliceous aggregate.

The present invention also includes an asphalt concrete comprising theproduct of combining an asphalt, a functionalized block copolymer, and asiliceous aggregate.

The present invention further includes a diblock copolymer comprising avinyl block comprising conjugated vinyl aromatic units, a diene blockcomprising conjugated diene units and substantially devoid of a taperedblock section between the vinyl block and the diene block wherein thediblock copolymer comprises a vinyl content of at least about 20%, and amolecular weight of at least about 50,000.

The present invention still further includes a method of preparing thediblock copolymer comprising anionically polymerizing a first charge ofdiene monomer with a functionalized initiator in the presence of a vinylmodifier thereby forming a polymer having a vinyl content, and wherebysaid polymerizing comprises consumption of substantially all of saiddiene monomer, and polymerizing a second charge of vinyl aromaticmonomer in the presence of said polymer forming a diblock copolymercomprising a diene block and a vinyl block, whereby said diblockcopolymer comprises a vinyl content of at least about 20%, and amolecular weight of at least about 50,000.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

In a first embodiment, the invention provides a modified asphaltcomposition that includes a naphthenic asphalt and high-vinyl blockcopolymer. This modified asphalt composition can be used to prepareasphalt concretes that are especially useful for paving roadways,highways, exit ramps, streets, driveways, parking lots, airport runwaysor airport taxiways utilizing conventional procedures.

It has been unexpectedly discovered that the mixture or combination ofnaphthenic asphalt and the high-vinyl block copolymer overcomes some ofthe shortcomings associated with modifying naphthenic asphalts. Inparticular, surprisingly good results have been observed as compared toasphalts modified with conventional block copolymers when thesecompositions are subjected to the Softening Point Separation Test, whichis preferred under the Superpave System of the Strategic HighwayResearch Program. It is believed that the high-vinyl block copolymer andthe naphthenic asphalt synergistically interact to provide theseadvantageous results. This is especially advantageous because naphthenicasphalt sources are strategically located around the globe andconventional block copolymers have proven to have a high degree ofseparation from these naphthenic asphalts.

Asphalts include bitumens that occur in nature or are obtained inpetroleum processing. Asphalts typically contain very high molecularweight hydrocarbons called asphaltenes, which are soluble in carbondisulfide, pyridine, aromatic hydrocarbons, chlorinated hydrocarbons,and THF. Asphalts or bituminous materials are typically solids,semi-solids or liquids, and a penetration test is typically employed forconsistency or viscosity. In this classification, solid materials arethose having a penetration at 25° C. under a load of 100 grams appliedfor 5 seconds, of not more than 10 decimillimeters (1 millimeter).Semi-solids are those having a penetration at 25° C. under a load of 100grams applied for 5 seconds of more than 10 decimillimeters (1millimeter) and a penetration at 25° C. under a load of 50 grams appliedfor 1 second of not more than 35 millimeters.

Naphthenic asphalt or bitumens are generally characterized by includinga net excess of acidic compounds. Preferably, the acid value (mg KOH/g)is about 1.5 to about 5. The base value (mg KOH/g) of naphthenicbitumens is preferably from about 0 to about 1.

One particularly useful source of naphthenic asphalt is obtained fromChina and the coastal regions thereof. Other sources of naphthenicasphalt include those obtained from South and Central America.

The high-vinyl block copolymer is preferably a diblock copolymer thatincludes one block including vinyl aromatic units and one blockincluding diene units. The vinyl aromatic block preferably includesvinyl aromatic units deriving from vinyl aromatic monomer. Useful vinylaromatics include those having 8 to about 20 carbon atoms such asstyrene, α-methylstyrene, p-methylstyrene, vinyl anthracene, and vinylnaphthalene; styrene is the preferred vinyl aromatic. The diene blockpreferably includes diene units deriving from conjugated dienes.Suitable conjugated dienes include those having from about 4 to about 12carbon atoms such as 1,3-butadiene, 1,3-cyclohexadiene, isoprene,1,3-pentadiene, 1,3-hexadiene, 2,3-dimethyl-1,3-butadiene,2-ethyl-1,3-butadiene, 2-methyl-1,3pentadiene, 3-methyl-1,3-pentadiene,4-methyl-1,3-pentadiene, and 2,4-hexadiene; 1,3-butadiene is thepreferred conjugated diene. The block copolymer may include a taperedsection, which includes both styrene and butadiene units. In preferredembodiments, the tapered section is minimized; in other words, the blockcopolymer includes less than 5% by weight, more preferably less than 3%by weight, and even more preferably less than 1% by weight of a taperedsection. In one embodiment, the block copolymer is devoid of a taperedsection.

The high-vinyl block copolymer is generally characterized by having aweight average molecular weight of at least 50 kg/mol, preferably atleast about 75 kg/mol, more preferably at least about 100 kg/mol, andeven more preferably at least about 125 kg/mol; also, the blockcopolymer has a weight average molecular weight that is 500 kg/mol orless, preferably 250 kg/mol or less, more preferably 200 kg/mol or less,and more preferably 150 kg/mol or less, as determined by GPC analysisusing polystyrene standards.

The block copolymer is also generally characterized by having amolecular weight distribution that is less than about 2, preferably lessthan about 1.5, more preferably less than about 1.2, and even morepreferably less than about 1.05.

In one embodiment, the high-vinyl block copolymer includes greater than10% by weight, in another embodiment, the high vinyl block copolymerincludes greater than 15% by weight, and in another embodiment, greaterthan 20% by weight, and in yet another embodiment, greater than 23% byweight vinyl aromatic units; also, in one embodiment, the blockcopolymer includes less than 50% by weight, and in another embodiment,less than 35% by weight, and in another embodiment, less than 30% byweight, and in yet another embodiment, less than 27% by weight vinylaromatic units. The remainder of the copolymer preferably includes thediene block.

The diene block is preferably characterized by including a vinyl content(i.e., 1,2 microstructure) that is preferably at least about 15% byweight, more preferably at least about 20% by weight, more preferably atleast 23% by weight, even more preferably at least about 25% by weight,and still more preferably at least about 27% by weight based upon theweight of the diene content of the block copolymer (i.e., the dieneblock). Also, in another particular embodiment, this diene block may becharacterized by a vinyl content that is preferably 34% by weight orless, more preferably 33% by weight or less, more preferably 32% byweight or less, and still more preferably 31% by weight or less, basedupon the weight of the diene content of the block copolymer.

The block copolymer is also generally characterized by having a gelcontent of less than about 1.5% by weight, preferably less than about1.2% by weight, more preferably less than about 1.0% by weight, andstill more preferably less than about 0.7% by weight as determined bythe amount of insoluble material when a sample is dissolved in tolueneat room temperature.

The high-vinyl block copolymers are preferably prepared by anionic,living polymerization techniques. Anionically-polymerized, livingpolymers are formed by reacting anionic initiators with certainunsaturated monomers to propagate a polymeric structure. Throughoutformation and propagation of the polymer, the polymeric structure isanionic and “living.” A new batch of monomer subsequently added to thereaction can add to the living ends of the existing chains and increasethe degree of polymerization. A living polymer, therefore, is apolymeric segment having a living or reactive end. Anionicpolymerization is further described in George Odian, Principles ofPolymerization, ch. 5 (3^(rd) Ed. 1991), or Panek, 94 J. Am. Chem. Soc.,8768 (1972), which are incorporated herein by reference.

The preparation technique employed in this embodiment preferablyincludes polymerization of a first block followed by the sequentialpolymerization of a second block. As those skilled in the art willappreciate, this sequential polymerization includes charging initiatorand monomer that will give rise to the first block, and once the monomergiving rise to the first block is consumed (or consumed to a desireddegree), monomer that will give rise to the second block cansubsequently be charged.

The diene block can be the first block synthesized or the vinyl aromaticblock can be the first block synthesized. In either event, in oneembodiment it is preferred that the monomer charged or provided forsynthesizing the first block be consumed to an extent such that taperingis limited as defined above. In preferred embodiments, at least 90%,more preferably at least 95%, even more preferably at least 98%, andstill more preferably at least 99% of the monomer available or chargedto the reactor for synthesizing the first block is consumed prior tocharging or providing the monomer for synthesizing the second block.

Any anionic initiator can be employed to initiate the formation andpropagation of the living polymers. Useful initiators includefunctionalized initiators, the residue of which will impart the head ofthe polymer with a functional group, as well as non-functionalizedinitiators. Exemplary anionic initiators include, but are not limitedto, alkyl lithium initiators such as n-butyl lithium, arenyllithiuminitiators, arenylsodium initiators, N-lithium dihydro-carbon amides,aminoalkyllithiums, and alkyl tin lithiums. Other useful initiatorsinclude lithiohexamethyleneimine, N-lithiohexamethyleneimide,N-lithiopyrrolidinide, and N-lithiododecamethyleneimide as well asorganolithium compounds such as the tri-alkyl lithium adducts ofsubstituted aldimines and substituted ketimines, and N-lithio salts ofsubstituted secondary amines. Exemplary initiators are also described inthe following U.S. Pat. Nos. 5,332,810, 5,329,005, 5,578,542, 5,393,721,5,698,646, 5,491,230, 5,521,309, 5,496,940, 5,574,109, 5,786,441, andInternational Publication No. WO 2004/020475, which are incorporatedherein by reference.

The amount of initiator employed in conducting anionic polymerizationscan vary widely based upon the desired polymer characteristics. In oneembodiment, it is preferred to employ from about 0.1 to about 100, andmore preferably from about 0.33 to about 10 mmol of lithium per 100 g ofmonomer.

Anionic polymerizations may be conducted in a polar solvent such astetrahydrofuran (THF) or a nonpolar hydrocarbon such as the variouscyclic and acyclic hexanes, heptanes, octanes, pentanes, their alkylatedderivatives, and mixtures thereof, as well as benzene.

In one embodiment, to control vinyl content within the elastomericsegment, a vinyl modifier may be added to the polymerizationingredients. Amounts range between o and go or more equivalents perequivalent of lithium. The amount depends on the amount of vinyldesired, the level of styrene employed and the temperature of thepolymerization, as well as the nature of the specific vinyl modifier(modifier) employed. Suitable polymerization modifiers include, forexample, ethers or amines to provide the desired microstructure andrandomization of the comonomer units. In one embodiment, about 30% ofthe polymer chains have an amine.

Compounds useful as vinyl modifiers include those having an oxygen ornitrogen heteroatom and a non-bonded pair of electrons. Examples includedialkyl ethers of mono and oligo alkylene glycols; “crown” ethers;tertiary amines such as tetramethylethylene diamine (TMEDA); linear THFoligomers; and the like. Specific examples of compounds useful as vinylmodifiers include tetrahydrofuran (THF), linear and cyclic oligomericoxolanyl alkanes such as 2,2-bis(2′-tetrahydrofuryl) propane,di-piperidyl ethane, dipiperidyl methane, hexamethylphosphoramide,N-N′-dimethylpiperazine, diazabicyclooctane, dimethyl ether, diethylether, tributylamine and the like. The linear and cyclic oligomericoxolanyl alkane modifiers (OOPs) are described in U.S. Pat. No.4,429,091, incorporated herein by reference.

Synthesis of the diene block, particularly synthesis of a polybutadieneblock by way of polymerizing 1,3-butadiene, preferably occurs in thepresence of a vinyl modifier. While certain modifiers may randomize thecopolymer when employed in particular amounts, in one embodiment theamount of vinyl modifier that is used is insufficient to randomize thecopolymer. Useful vinyl modifiers include OOPs. Those skilled in the artwill be able to readily select the amount of vinyl modifier that will beuseful in achieving the desired properties set forth above. For example,when a OOPs vinyl modifier is employed, the amount present within thepolymerization is generally from about 0.001 to about 1.0 and based uponthe amount of lithium charged into the reactor.

Anionically polymerized living polymers can be prepared by either batchor continuous methods. A batch polymerization is preferably begun bycharging monomer and solvent to a suitable reaction vessel, followed bythe addition of the vinyl modifier (if employed) and an initiatorcompound. The vinyl modifier or the initiator may be added in eitherorder to the monomer in the reaction vessel. The reactants arepreferably heated to a temperature of from about 20 to about 130° C. andthe polymerization is allowed to proceed for from about 0.1 to about 24hours. This reaction preferably produces a reactive polymer having areactive or living end. Preferably, at least about 30% of the polymermolecules contain a living end. More preferably, at least about 50% ofthe polymer molecules contain a living end. Even more preferably, atleast about 80% contain a living end.

In preferred embodiments, a terminating agent or quenching compound isadded to the polymerization medium in order to terminate thepolymerization reaction. In general, the addition of these agents orcompounds neutralizes the anionic nature of the living polymer. In oneembodiment, the polymerization is quenched by the addition of a protondonor that can protonate the living polymer. Exemplary proton donorsinclude isopropyl alcohol. These proton donors typically includenon-functionalized terminating or quenching agents that simply providethe terminal end of the polymer with a hydrogen atom. In otherembodiments, functionalized terminating agents are employed. Theseterminating agents typically neutralize the anionic character of theliving polymer by adding to the terminal end of the polymer and leave afunctional group at the terminal end. Numerous terminating agents areknown and practice of this embodiment is not limited by the selection ofany particular terminating agent.

After formation of the block copolymer, a processing aid or otheroptional additives such as oil can be added to the polymer cement. Inone particular embodiment, the polymer is oil extended. In anotherparticular embodiment, the polymer is extended to about 10 to 20%extended. Oil extending the polymer is advantageous in that it increasessolubility of the polymer during subsequent manufacturing processes, andspeeds the rate at which the polymer dissolves during subsequentmanufacturing processes such as mixing the polymer and curing agent withasphalt. The block copolymer and other optional ingredients are thenisolated from the solvent and are preferably dried. Conventionalprocedures for desolventization and drying may be employed. In oneembodiment, the block copolymer may be isolated from the solvent bysteam desolventization or hot water coagulation of the solvent followedby filtration. Residual solvent may be removed by using conventionaldrying techniques such as oven drying or drum drying. Alternatively, thecement may be directly drum dried.

Curing agents can be added to the modified asphalt compositions of thisembodiment. Curing agents often used in asphalt compositions includephenolic resins and elemental sulfur. One preferred curing agent is abismaleimide curing agent, which is described in U.S. Pat. No.6,486,236, which is incorporated herein by reference. Conventionalamounts may be employed in practicing this invention.

In one embodiment, a premix includes a curing agent added to the blockcopolymer without completely curing the polymer. The gel content of thepolymer increases as the polymer is cured. The gel content may beindicated by measuring the relative weight of polymer that is insolublein toluene at room temperature. In one embodiment, the curing agent isadded without substantially increasing the gel content of the polymer.In another embodiment, the curative, in solution with hexane, is addedto the completed polymerization reaction after the addition of theterminating agent. The polymer and curative are mixed at about 200° F.for about 5½ minutes. In one particular embodiment, before the solventis removed and the polymer is dried, the polymer is oil extended. In oneparticular embodiment the polymer is extended to about 10 to 20%extended. In this embodiment, the curing agent may be present during theextending of the polymer. Oil extending is advantageous in that itincreases solubility of the polymer during subsequent manufacturingprocesses, and speeds the rate at which the polymer dissolves duringsubsequent manufacturing processes such as mixing the polymer and curingagent with asphalt.

Suitable curing agents include Sulfur, Santocure (available fromFlexsys, of Akron, Ohio), ZnO, Stearic Acid, HVA-2 (available fromDuPont of Delaware), Vanax PY (available from R.T. Vanderbilt ofConnecticut), Slufasan (available from Flexsys, of Akron, Ohio), andPAXL (available from ATOFina of Philadelphia, Pa.). In one embodiment,the amount of curing agent is less than about 2%, in another embodimentless than about 1%, in a further embodiment less than about 0.5%, and inyet another embodiment about 0.2%.

A premix is more desirable than mixing the curing agent along with theother components of the PMA because less time is required to mix thepremix and asphalt than is required to mix the polymer, asphalt and curepackage. Another benefit is that less curing agent is required in thepremix than if the curative, asphalt, and polymer are added as separatecomponents. Typically, if the curative and polymer are added to theasphalt as separate components, the end user of the asphalt would mix atleast the asphalt, polymer and curative. Another advantage to the premixis that the end user would need to add one fewer ingredient, resultingin less opportunity for error in mixing.

The modified asphalt compositions of this embodiment may also includethose other ingredients or constituents that are commonly employed inthe industry. For example, the compositions may include anti-strippingcompounds, fibers, release agents, and fillers. Some specific examplesof additives that can be employed include kaolin clay, calciumcarbonate, bentonite clay, sanders dust and cellulose fibers.

The modified asphalt compositions of this embodiment can be prepared byusing conventional techniques. This typically includes blending theasphalt with a desired amount of block copolymer at a desiredtemperature. This mixing step can occur prior to or in conjunction withthe addition of a curative or the other additives. In one embodiment,the block copolymer is dissolved in molten asphalt at temperaturesgreater than about 120 C. Mixing is preferably continued for about 25 toabout 400 minutes at a temperature of about 145 to about 205 C.(preferably from about 160 to about 193 C.). Preferably, a homogeneousmixture is obtained.

The asphalt compositions of this embodiment include at from about 0.1 toabout 10 parts by weight (pbw), in another embodiment the asphaltcompositions include from about 0.3 to about 5 pbw, and in anotherembodiment, from about 3 to about 6 pbw of the block copolymer per 100parts by weight of the asphalt.

The modified asphalt compositions of this embodiment may be employed toprepare asphalt concrete compositions that include the modified asphaltand an aggregate. Conventional aggregate that is used in the pavingindustry can be utilized in the practice of this embodiment. Aggregatetypically includes rocks, stones, crushed stone, gravel, sand, silica,or mixtures of one more thereof. Specific examples of aggregates includemarble, limestone, basalt, dolomite, sandstone, granite, and quartzite.

Aggregate typically has a wide distribution of particle sizes rangingfrom dust to golf ball size. The best particle size distribution variesfrom application to application. In certain embodiments, it may beadvantageous to coat the aggregate with latex in accordance with theteachings of U.S. Pat. No. 5,262,240, which is incorporated herein byreference, to improve resistance to stripping by water.

The asphalt concrete, which is prepared by mixing the modified asphaltwith aggregate, can be prepared by using standard equipment andprocedures. In one or more embodiments, the aggregate is mixed with theasphalt to attain an essentially homogeneous asphalt concrete. Forinstance, the aggregate can be mixed with asphalt to produce asphaltconcrete on a continuous basis in a standard mixer.

When preparing an asphalt concrete, generally from about 1 weightpercent to about 10 weight percent of the modified asphalt and fromabout go weight percent to about 99 weight percent aggregate (based onthe total weight of the asphalt concrete) is mixed. Preferably, theasphalt concrete contains from about 3 weight percent to about 8 weightpercent of the modified asphalt cement and from about 92 weight percentto about 97 weight percent of the aggregate. More preferably, theasphalt concrete contains from about 4 weight percent to about 7 weightpercent of the modified asphalt cement and from about 93 weight percentto about 96 weight percent of the aggregate.

In a second embodiment, the invention provides an asphalt concretecomposition that includes an asphalt, a functionalized block copolymer,and a siliceous aggregate. This asphalt concrete is especially usefulfor paving roadways, highways, exit ramps, streets, driveways, parkinglots, airport runways or airport taxiways utilizing conventionalprocedures.

It has been unexpectedly discovered that the use of the functionalizedblock copolymer can alleviate some of the shortcomings that areassociated with the use of siliceous aggregate in preparing asphaltconcrete. In particular, the resulting pavement is surprisinglycharacterized by less cracking and crumbling than similar pavements thatemploy siliceous aggregated and unfunctionalized block copolymer andunfunctionalized block copolymers. It is believed that the siliceousaggregate synergistically interacts with the functionalized blockcopolymer to provide these advantageous results. These advantages canprove to be significant inasmuch as many sources of siliceous aggregatecan be found around the globe and the use of siliceous aggregate couldprove to be technologically useful.

The functionalized block copolymer includes at least one diene block, atleast one vinyl aromatic block, and at least one terminal functionalgroup. The functional group may be located at the head or tail of theblock copolymer and may be attached to either the diene block or thevinyl aromatic block. In one embodiment, the functionalized blockcopolymer includes two terminal functional groups positioned at oppositeends of the copolymer. While the block copolymer may include variousmolecular architectures including triblocks, the preferredfunctionalized block copolymers include di-blocks that include oneelastomeric block and one thermoplastic block.

In one embodiment, the functionalized block copolymer can be defined bythe formula Iα-Π-θ-ωwhere α is a hydrogen atom or a functional group, Π is a diene block, θis a vinyl aromatic block, and ω is a hydrogen atom or a functionalgroup, with the proviso that at least one of α or ω is a functionalgroup.

The vinyl aromatic block preferably includes vinyl aromatic unitsderiving from vinyl aromatic monomer. Useful vinyl aromatics includethose having 8 to about 20 carbon atoms such as styrene,α-methylstyrene, p-methylstyrene, vinyl anthracene, and vinylnaphthalene; styrene is the preferred vinyl aromatic. The diene blockpreferably includes diene units deriving from conjugated dienes.Suitable conjugated dienes include those having from about 4 to about 12carbon atoms such as 1,3-butadiene, 1,3-cyclohexadiene, isoprene,1,3-pentadiene, 1,3-hexadiene, 2,3-dimethyl-1,3-butadiene,2-ethyl-1,3-butadiene, 2-methyl-1,3 pentadiene, 3-methyl-1,3-pentadiene,4-methyl-1,3-pentadiene, and 2,4-hexadiene; 1,3-butadiene is thepreferred conjugated diene. The block copolymer may include a taperedsection, which includes both styrene and butadiene units. In preferredembodiments, the tapered section is minimized; in other words, the blockcopolymer includes less than 5% by weight, more preferably less than 3%by weight, and even more preferably less than 1% by weight of a taperedsection. In one embodiment, the block copolymer is devoid of a taperedsection.

The functionalized block copolymer is generally characterized by havinga weight average molecular weight of at least 50 kg/mol, preferably atleast about 75 kg/mol, more preferably at least about 100 kg/mol, andeven more preferably at least about 125 kg/mol; also, the blockcopolymer has a weight average molecular weight that is 500 kg/mol orless, preferably 250 kg/mol or less, more preferably 200 kg/mol or less,and more preferably 150 kg/mol or less, as determined by GPC analysisusing polystyrene standards.

The block copolymer is also generally characterized by having amolecular weight distribution that is less than about 2, preferably lessthan about 1.5, more preferably less than about 1.2, and even morepreferably less than about 1.05.

The vinyl block copolymer, in one embodiment, includes greater than 5%by weight, and in one embodiment, greater than 10% by weight, and inanother embodiment greater than 20% by weight, and in yet anotherembodiment, greater than 23% by weight vinyl aromatic units; also, theblock copolymer in one embodiment includes less than 45% by weight, andin another embodiment less than 35% by weight, and in another embodimentless than 30% by weight, and in yet another embodiment less than 27% byweight vinyl aromatic units. The remainder of the copolymer preferablyincludes the diene block.

The diene block in one embodiment includes a vinyl content (i.e., 1,2microstructure) that is at least about 15% by weight, and in anotherembodiment at least about 20% by weight, and in another embodiment atleast 23% by weight, and in another embodiment at least about 25% byweight, and in yet another embodiment at least about 27% by weight basedupon the entire weight of the functionalized block copolymer. Also, thisdiene block is characterized by a vinyl content that in one embodimentincludes 34% by weight or less, and in another embodiment, 33% by weightor less, and in another embodiment, 32% by weight or less, and in yetanother embodiment 31% by weight or less, based on the entire weight ofthe diene block.

The block copolymer is also generally characterized by having a gelcontent of less than about 1.5% by weight, preferably less than about1.2%. by weight, more preferably less than about 1.0% by weight, andstill more preferably less than about 0.7% by weight as determined bythe amount of insoluble material when a sample is dissolved in tolueneat room temperature.

In one or more embodiments, the functional group α or ω includes thosegroups or substituents that can react or interact with siliceousaggregate. In one embodiment, these groups or substituents arecharacterized by the ability to chemically bond with the siliceousaggregate. The preferred functional groups include silicon-containingfunctional groups. Accordingly, a preferred functionalized blockcopolymer can be defined by the formula II[Block Copolymer]-Si(R¹)₃where each R¹ is individually selected from hydrocarbyl, substitutedhydrocarbyl, or alkoxy groups. Preferably, at least on R¹ is an alkoxygroup. In preferred embodiments, the functional group α or ω includes asilyl group that is attached to the elastomeric block, which ispreferably a polybutadiene block.

The hydrocarbyl or substituted hydrocarbyl group includes, but is notlimited to, alkyl, cycloalkyl, substituted cycloalkyl, alkenyl,cycloalkenyl, substituted cycloalkenyl, aryl, allyl, substituted aryl,aralkyl, alkaryl, and alkynyl groups, with each group preferablycontaining from 1 carbon atom, or the appropriate minimum number ofcarbon atoms to form the group, up to 20 carbon atoms. These hydrocarbylgroups may contain heteroatoms such as, but not limited to, nitrogen,boron, oxygen, silicon, sulfur, and phosphorus atoms.

The alkoxy groups may be defined by the formula OR, where R is amonovalent organic group that is preferably a hydrocarbyl or substitutedhydrocarbyl group.

Exemplary silicon-containing groups include trimethoxysilyl,triethoxysilyl, tripropoxysilyl, tri t-butyoxysilyl,dimethyoxymethylsilyl, diethoxy ethylsilyl, dipropoxypropylsilyl, trit-butoxybutylsilyl, and triphenoxysilyl groups; the preferred functionalgroup includes triethoxysilyl groups.

The functionalized elastomeric block copolymers are preferably preparedby employing anionic, living-polymerization techniques, which aredisclosed above. The functional group can be attached to the copolymerhead by use of a functionalized initiator, to the copolymer tail by useof a functional terminating agent, or to both the copolymer head andtail by use of both a functional initiator and a functionalizedterminating agent. The functional group is preferably attached to thetail or terminus of the living polymer by employing a functionalizedterminating agent. The terminating agent is preferably added after peakpolymerization temperature has been achieved for the second charge ofmonomer (i.e., the charge that gives rise to the second block). Inpreferred embodiments, the terminating agent is added to thepolymerization medium within 30 minutes, more preferably within 15minutes, and even more preferably within 7.5 minutes of the peakpolymerization temperature resulting from the second charge of monomer.

Useful terminating agents include, but are not limited to, thoserepresented by the formula(R¹)_(4-z)Si(OR²)_(z)where R¹ is independently a halogen or a hydrocarbyl or substitutedhydrocarbyl group, each R² is independently a hydrocarbyl or substitutedhydrocarbyl group, and z is an integer from 1 to 4. Suitable examples ofsiloxane terminating agents include tetraalkoxysilanes,alkylalkoxysilanes, arylalkoxysilanes, alkenylalkoxysilanes, andhaloalkoxysilanes.

Examples of tetraalkoxysilane compounds include tetramethylorthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate,tetrabutyl orthosilicate, tetra(2-ethylhexyl) orthosilicate, tetraphenylorthosilicate, tetratoluyloxysilane, and the like.

Examples of alkylalkoxysilane compounds include methyltrimethoxysilane,methyltriethoxysilane, methyltri-n-propoxysilane,methyltri-n-butoxysilane, methyltriphenoxysilane, ethyltrimethoxysilane,ethyltriethoxysilane, ethyltri-n-propoxysilane, ethyltri-n-butoxysilane,ethyltriphenoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane,dimethyldi-n-propoxysilane, dimethyldi-n-butoxysilane,dimethyldiphenoxysilane, diethyldimethoxysilane,diphenyldimethoxysilane, 3-glycidoxypropyltrimethoxysilane (GPMOS),γ-methacryloxy propyl trimethoxysilane and the like.

Examples of arylalkoxysilane compounds include phenyltrimethoxysilane,phenyltriethoxysilane, phenyltri-n-propoxysilane,phenyltri-n-butoxysilane, phenyltriphenoxysilane, and the like.

Examples of alkenylalkoxysilane compounds include vinyltrimethoxysilane,vinyltriethoxysilane, vinyltri-n-propoxysilane, vinyltri-n-butoxysilane,vinyltriphenoxysilane, allyltrimethoxysilane, octenyltrimethoxysilane,divinyldimethoxysilane, and the like.

Examples of haloalkoxysilane compounds include trimethoxychlorosilane,triethoxychlorosilane, tri-n-propoxychlorosilane,tri-n-butoxychlorosilane, triphenoxychlorosilane,dimethoxydichlorosilane, diethoxydichlorosilane,di-n-propoxydichlorosilane, diphenoxydichlorosilane,methoxytrichlorosilane, ethoxytrichlorosilane, n-propoxytrichlorosilane,phenoxytrichlorosilane, trimethoxybromosilane, triethoxybromosilane,tri-n-propoxybromosilane, triphenoxybromosilane, dimethoxydibromosilane,diethoxydibromosilane, di-n-propoxydibromosilane,diphenoxydibromosilane, methoxytribromosilane, ethoxytribromosilane,n-propoxytribromosilane, phenoxytribromosilane, trimethoxyiodosilane,triethoxyiodosilane, tri-n-propoxyiodosilane, triphenoxyiodosilane,dimethoxydiiodosilane, di-n-propoxydiiodosilane, diphenoxydiiodosilane,methoxytriiodosilane, ethoxytriiodosilane, n-propoxytriiodosilane,phenoxytriiodosilane, and the like.

Other useful silanes include bis-(trimethoxysilane)-ether,3-mercaptopropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane,3,3′-bis (triethoxysilylpropyl) disulfide, Si-69(bis-(3-triethoxysilylpropyl)tetrasulfide) and the like.

Preferred hydroalkyoxy silane terminating agents include tetraethylorthosilicate.

In one embodiment, siliceous aggregate is generally characterized byincluding at least 30% by weight, in another embodiment at least atleast 40% by weight, in still another embodiment at least 50% by weight,in yet another embodiment at least 60% by weight, in another embodimentat least 70% by weight, in still another embodiment at least 80% byweight, and in yet another embodiment at least 90% by weight silica(i.e., silicon dioxide). Exemplary siliceous aggregates includingsandstone, granite, quartzite, flint, and diatomite.

Besides the use of the functionalized block copolymer and the siliceousaggregate, the asphalt concretes of this embodiment may be prepared in aconventional manner. Accordingly, in one embodiment, the functionalizedblock copolymer is added to an asphalt in order to prepare a modifiedasphalt composition. Virtually any type of asphalt can be employed inmaking the modified asphalt of this embodiment. Asphalt has beengenerically disclosed above; asphalt is also generically disclosed inU.S. Pat. Nos. 4,145,322, 5,955,537, and 5,986,010 and U.S. PublicationNos. 2003/0191212 A1, which are all incorporated herein by reference.

This modified asphalt, which includes the functionalized blockcopolymer, is then combined with the siliceous aggregate to form theasphalt concrete of this embodiment. As is conventional in the art, themodified asphalt and/or asphalt concrete may include other additivesthat are conventionally employed in the art including, but not limitedto, curatives and the like.

The methods employed to prepare either the modified asphalt or theasphalt concrete include those procedures that are conventional in theart and therefore the disclosure above with respect to the firstembodiment is relied on for a description of these techniques.

The amount of functionalized block copolymer employed may vary. In oneembodiment, and with reference to the preparation of a modified asphaltcomposition, the modified asphalt may include at least about 0.001% byweight, more preferably at least about 1.0% by weight, and even morepreferably at least about 3.0% by weight of the functionalized blockcopolymer based on the entire weight of the modified asphaltcomposition; on the other hand, the modified asphalt compositionpreferably includes less than about 10% by weight, more preferably lessthan about 8% by weight, and even more preferably less than about 6% byweight of the functionalized block copolymer based upon the entireweight of the modified asphalt.

The amount of functionalized block copolymer may also be described withreference to the asphalt concrete. In one embodiment, the asphaltconcrete includes preferably at least about 0.001% by weight, morepreferably at least about 1.0% by weight, and even more preferably atleast about 3.0% by weight functionalized block copolymer based upon theentire weight of the asphalt concrete; on the other hand, the asphaltconcrete preferably includes less than about 10% by weight, morepreferably less than about 8% by weight, and even more preferably lessthan about 6% by weight functionalized block copolymer based on theentire weight of the asphalt concrete.

The asphalt concrete preferably includes at least about 57% by weight,more preferably at least about 75% by weight, and even more preferablyat least about 90% by weight of the siliceous aggregate based upon theentire weight of the asphalt concrete; on the other hand, the asphaltconcrete preferably includes at less than about 99% by weight, morepreferably less than about 95% by weight, and even more preferably lessthan about 93% by weight siliceous aggregate based on the entire weightof the asphalt concrete.

Practice of this embodiment does not generally alter the amount of otheringredients that are employed in the preparation of the modified asphaltor the asphalt concrete. For example, the asphalt concrete may includeconventional amounts of asphalt, which are known in the art and aregenerally described hereinabove with respect to the first embodiment.The asphalt concrete may also include other aggregates that are known inthe art including those described herein.

Various modifications and alterations that do not depart from the scopeand spirit of this invention will become apparent to those skilled inthe art. This invention is not to be duly limited to the illustrativeembodiments set forth herein.

1. A modified asphalt composition comprising: a naphthenic asphalt; and a high-vinyl block copolymer.
 2. The composition of claim 1, where the naphthenic asphalt comprises a net excess of acidic compounds.
 3. The composition of claim 2, where the naphthenic asphalt comprises an acid value of from about 1.5 to about 5 mg KOH/g.
 4. The composition of claim 1, where the high-vinyl block copolymer comprises a diblock copolymer that comprises one block including vinyl aromatic units and one block comprising diene units.
 5. The composition of claim 4, where the block copolymer is substantially devoid of a tapered section.
 6. The composition of claim 4, where the block copolymer comprises a styrene content that is greater than about 10% by weight of the block copolymer.
 7. The composition of claim 4, where the block copolymer comprises a weight average molecular weight of at least 50 kg/mol and a molecular weight distribution of less than about
 2. 8. The composition of claim 4, where the diene block comprises at least about 15% by weight of its units in the vinyl configuration.
 9. The composition of claim 4, wherein a gel content of the block copolymer comprises less than about 1.5% by weight when tested by the toluene insoluble test.
 10. The composition of claim 1, wherein the high-vinyl block copolymer further comprises a curing agent.
 11. An asphalt concrete comprising: an asphalt; a functionalized block copolymer; and a siliceous aggregate.
 12. The asphalt concrete of claim 11, where the functionalized block copolymer includes at least one diene block, at least one vinyl aromatic block, and at least one terminal functional group.
 13. The asphalt concrete of claim 12, where the functionalized block copolymer is defined by the formula α-π-θ-ω where α comprises a hydrogen atom or a functional group, π comprises a diene block, θ comprises a vinyl aromatic block, and ω comprises a hydrogen atom or a functional group, wherein at least one of α or α comprise a functional group.
 14. The asphalt concrete of claim 13, where the diene block comprises units deriving from conjugated dienes and where the vinyl aromatic block comprises groups deriving from vinyl aromatic monomer.
 15. The asphalt concrete of claim 14, where the at least one functional group comprises a silicon-containing group.
 16. The asphalt concrete of claim 18, wherein the at least one terminal functional group comprises the formula Si(R¹)₃ where each R¹ comprises one of the group consisting of hydrocarbyl, substituted hydrocarbyl, and alkoxy groups.
 17. The asphalt concrete of claim 15, where the silicon-containing group comprises a siloxane derived compound comprising the formula (R¹)_(4-z)Si(OR²)_(z) where each R¹ comprises one of the group consisting of a halogen, a hydrocarbyl and a substituted hydrocarbyl group, each R² comprises either a hydrocarbyl or substituted hydrocarbyl group, and z comprises an integer from 1 to
 4. 18. A diblock copolymer comprising: a vinyl aromatic block comprising conjugated vinyl aromatic units; a diene block comprising conjugated diene units and substantially devoid of a tapered block section between the vinyl aromatic block and the diene block wherein the diblock copolymer comprises a vinyl content of at least about 15%, and a molecular weight of at least about 50,000.
 19. The diblock copolymer of claim 18, where the styrene content comprises from about 25% by weight of the diblock copolymer to about 35% by weight of the diblock copolymer.
 20. The diblock copolymer of claim 18, where the diblock copolymer comprises a molecular weight distribution of less than about 1.2.
 21. The diblock copolymer of claim 20, where the weight average molecular weight comprises from about 100 kg/mol to 500 kg/mol.
 22. The diblock copolymer of claim 21, where the gel content comprises less than about 1% by weight when tested by the toluene insoluble test.
 23. The diblock copolymer of claim 18, further wherein the block copolymer comprises a functional group attached to either the vinyl block or the diene block.
 24. The diblock copolymer of claim 23, where the functional group comprises a silicon-containing functional group.
 25. The diblock copolymer of claim 24, where the silicon-containing functional group comprises the formula Si(R¹)₃ where each R¹ comprises one of the group consisting of hydrocarbyl, substituted hydrocarbyl, and alkoxy groups.
 26. A method of preparing a diblock copolymer comprising: anionically polymerizing a first charge of diene monomer with a functionalized initiator in the presence of a vinyl modifier thereby forming a polymer having a vinyl content, and whereby said polymerizing comprises consumption of substantially all of said diene monomer; and polymerizing a second charge of vinyl aromatic monomer in the presence of said polymer forming a diblock copolymer comprising a diene block and a vinyl block, whereby said diblock copolymer comprises a vinyl content of at least about 20%, and a molecular weight of at least about 50,000.
 27. The method of claim 26, where the consumption of said diene monomer comprises at least 90% of the first-polymerized monomer.
 28. The method of claim 26, where the amount of vinyl modifier present comprises less than an amount necessary to randomize the vinyl aromatic monomer or the diene monomer.
 29. The method of claim 26, further comprising functionalizing the copolymer with a silicon-containing functional group of the formula Si(R¹)₃ where each R¹ comprises one of the group consisting of hydrocarbyl, substituted hydrocarbyl, and alkoxy groups. 